Fibroblast proliferation
and subconjunctival fibrosis are the main reasons for failure of filtering
surgery. Asians have been reported to have more severe tissure reactions than
white people, possibly leading to poorer surgical outcome compared to whites.
With this in mind, can drainage tube perform in Asians eyes as well as in
non-Asian patients?
Recently,the clinical outcomes of the Asian eyes that received both non-valved
and vaved devices have been reported. In addition, the use of antimetabolites
in drainage tubes among Asian eyes have been addressed and further studies in
their role are to be warranted in the future.
Although exact comparison between studies is difficult because of different
criteria for success and patient population, reported success rates in both
non-valved and valved tubes in non-Asian eyes ranged from 65% to 90 %.t Study
using non-valved tubes including Molteno and Baerveldt among Asian eyes
reported 85.5 % success rate at approximately 13 month of follow-up with low
postoperative complication. A retrospective study using the Ahmed glaucoma
valve implant also revealed 73.8 % success outcome comparable with those
reported in non-Asian eyes at 22 months of follow-up. However, formation of
postoperative encapsulated bleb was more commonly noted. Use of antimetabolite
such as mitomycin-C in the Ahmed drainage tube appeared to be effective (77%
success rate at 2 year follow-up) in Asian eyes with a significant proportion
of patients having neovascular glaucoma (45%) without increased complication
rates.
Based on these repors, drainage tubes do well in Asian population in that the
success rate for intraocular pressure control and complication rate do not
differ from other published series in non-Asian eyes except frequent occurrence
of encapsulated bleb as noted with the Ahmed glaucoma tubes.This may represent
a more aggressive tissure healing process in the Asian eyes or tendency of
intense fibrous reaction seen in eyes with neovascular glaucoma. Further
studies are needed to confirm and overcome this phenomenon.